Breakthrough in basin modeling using time/space frame

International audienceA new way to model basins that couples the new space-time mathematical framework (defined as the UVT transform) and 3D restoration allows for easy and realistic construction of 4D models. Using models built with the UVT transform, basin modelers will not only include faults and erosional surface properly in all structural settings, but also restore them using a 3D geomechanical finite element engine to model the proper paleo-basin geometries. As the UVT model is being restored, a "hybrid" grid carrying the static and dynamic properties is fully restored. The basin simulation software then takes all the time-dependent geological models and performs its computations on the 4D grid. The goals of basin modeling are to find out whether the oil window was reached, to locate possible traps, and to estimate the volume and quality of hydrocarbons initially generated, migrated, and trapped, as well as to estimate pressure and temperatures in the reservoir (Rudkiewicz et al., 2000). To achieve this, a full subsurface geologic model must be constructed and restored from the source rock to the current topography. Currently, a 4D basin model is a simple horizon based layer cake grid where faults are not represented explicitly as discontinuities. The reconstruction through time is based on the vertical back-stripping of layers. This is limited because the displacement of the blocks along the fault planes cannot be modeled and the material on both sides of reverse faults cannot be represented. The estimation of migration paths across faults can be inaccurate especially in compressive basins or in extensive basins with long offset listric faults.In addition to the limitations in properly representing the model at a given time step, the evolution of the basin as a function of time is done through the simple back-stripping and flattening of layers. So, this paleo-basin geometry can be inaccurate

Mechanisms for high pressures and high temperatures in the Central North Sea Graben

Rudkiewicz Jean-Luc, Vear Alwyn, Düppenbecker Stephan, Brigaud Frédéric. Mechanisms for high pressures and high temperatures in the Central North Sea Graben. In: Transferts dans les systèmes sédimentaires : de l'échelle du pore à celle du bassin. Réunion spécialisée SGF-TRABAS/CNRS, Paris 27-28 septembre 1999. Résumés. Strasbourg : Institut de Géologie – Université Louis-Pasteur, 1999. pp. 127-128. (Sciences Géologiques. Mémoire, 99

Insights in Fault Flow Behaviour from Onshore Nigeria Petroleum System Modelling

Faults are complex geological features acting either as permeability barrier, baffle or drain to fluid flow in sedimentary basins. Their role can be crucial for over-pressure building and hydrocarbon migration, therefore they have to be properly integrated in basin modelling. The ArcTem basin simulator included in the TemisFlow software has been specifically designed to improve the modelling of faulted geological settings and to get a numerical representation of fault zones closer to the geological description. Here we present new developments in the simulator to compute fault properties through time as a function of available geological parameters, for single-phase 2D simulations. We have used this new prototype to model pressure evolution on a siliciclastic 2D section located onshore in the Niger Delta. The section is crossed by several normal growth faults which subdivide the basin into several sedimentary units and appear to be lateral limits of strong over-pressured zones. Faults are also thought to play a crucial role in hydrocarbons migration from the deep source rocks to shallow reservoirs. We automatically compute the Shale Gouge Ratio (SGR) along the fault planes through time, as well as the fault displacement velocity. The fault core permeability is then computed as a function of the SGR, including threshold values to account for shale smear formation. Longitudinal fault fluid flow is enhanced during periods of high fault slip velocity. The method allows us to simulate both along-fault drainages during the basin history as well as overpressure building at present-day. The simulated pressures are at first order within the range of observed pressures we had at our disposal

Structure et subsidence de la marge tethysienne entre Grenoble et Briancon au Lias et au Dogger

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Insights in Fault Flow Behaviour from Onshore Nigeria Petroleum System Modelling

Faults are complex geological features acting either as permeability barrier, baffle or drain to fluid flow in sedimentary basins. Their role can be crucial for over-pressure building and hydrocarbon migration, therefore they have to be properly integrated in basin modelling. The ArcTem basin simulator included in the TemisFlow software has been specifically designed to improve the modelling of faulted geological settings and to get a numerical representation of fault zones closer to the geological description. Here we present new developments in the simulator to compute fault properties through time as a function of available geological parameters, for single-phase 2D simulations. We have used this new prototype to model pressure evolution on a siliciclastic 2D section located onshore in the Niger Delta. The section is crossed by several normal growth faults which subdivide the basin into several sedimentary units and appear to be lateral limits of strong over-pressured zones. Faults are also thought to play a crucial role in hydrocarbons migration from the deep source rocks to shallow reservoirs. We automatically compute the Shale Gouge Ratio (SGR) along the fault planes through time, as well as the fault displacement velocity. The fault core permeability is then computed as a function of the SGR, including threshold values to account for shale smear formation. Longitudinal fault fluid flow is enhanced during periods of high fault slip velocity. The method allows us to simulate both along-fault drainages during the basin history as well as overpressure building at present-day. The simulated pressures are at first order within the range of observed pressures we had at our disposal

Thermal and structural modeling of the Scillato wedge-top basin source-to-sink system: Insights into the Sicilian fold-and-thrust belt evolution (Italy)

International audienceTemperature-dependent clay mineral assemblages, vitrinite reflectance, and one-dimensional (1-D) thermal and three-dimensional (3-D) geological modeling of a Neogene wedge-top basin in the Sicilian fold-and-thrust belt and its pre-orogenic substratum allowed us to: (1) define the burial history of the sedimentary succession filling the wedge-top basin and its substratum, (2) reconstruct the wedge-top basin geometry, depocenter migration, and sediment provenance through time in the framework of a source-to-sink system, and (3) shed new light into the kinematic evolution of the Apennine-Maghrebian fold-and-thrust belt.The pre-orogenic substratum of the Scillato basin shows an increase in levels of thermal maturity as a function of stratigraphic age that is consistent with maximum burial to 3.5 km in deep diagenetic conditions. In detail, Ro% values range from 0.40% to 0.94%, and random ordered illite-smectite (I-S) first converts to short-range ordered structures and then evolves to long-range ordered structures at the base of the Imerese unit. The wedge-top basin fill experienced shallow burial (∼2 km) and levels of thermal maturity in the immature stage of hydrocarbon generation and early diagenesis. Vitrinite reflectance and mixed-layer I-S values show two populations of authigenic and inherited phases. The indigenous population corresponds to macerals with Ro% values of 0.33%–0.45% and I-S with no preferred sequence in stacking of layers, whereas the reworked group corresponds to macerals with Ro% values of 0.42%–0.47% and short-range ordered I-S with no correlation as a function of depth.Authigenic and reworked components of the Scillato basin fill allowed us to unravel sediment provenance during the Neogene, identifying two main source areas feeding the wedge-top basin (crystalline units of the European domain and sedimentary units of the African domain), and to detect an early phase of exhumation driven by low-angle extensional faults that predated Neogene compression

Structural modeling based on sequential restoration of gravitational salt deformation in the Santos Basin (Brazil)

International audienceThe structural restoration of two parallel cross-sections in the central portion of the Santos Basin enablesa first understanding of existent 3D geological complexities. Santos Basin is one of the most proliferousbasins along the South Atlantic Brazilian margin. Due to the halokinesis, geological structures presentsignificant horizontal tectonic transport. The two geological cross-sections extend from the continental shelfto deep waters, in areas where salt tectonics is simple enough to be solved by 2D restoration. Such crosssectionsdisplay both extensional and compressional deformation. Paleobathymetry, isostatic regionalcompensation, salt volume control and overall aspects related to structural stylewere used to constrain basicboundary conditions. Several restoration algorithms, such as simple shear, flexural slip and free methods,were used to restore the sedimentary deformation, including salt gravity gliding. The results of the 2Drestoration are consistent with five major sequences of sedimentary evolution: (1) the brittle pre-saltdeformation, (2) the significant and fast salt deposition, (3) the initial post-salt deformation with predominantrafting tectonics, (4) the Late Cretaceous progradational deposition and coeval development ofcompressional minibasins, and (5) the Cenozoic sedimentary deposition, with less intense salt tectonics. A1D subsidence analysis based on the 2D restored results is shown as a useful restoration control tool. The 1Dresults indicate that an initially proximal infill evolves towards distal regions under salt tectonics control. The1D diagrams also record the history of the overburden movements through lateral depocenter migration inminibasins areas, submitted to large horizontal salt spreading. The results highlight an important isostaticmovement during salt deposition, large but not enough to eliminate a needed depression to accommodatethe thick evaporites. By quantifying the halokinetic lateral deformation through time, the results suggest lessintensity of the phenomenon throughout the Paleogene, with minor impacts on the petroleumsystemin thisperiod

3D structural modeling and restoration of the Apennine-Maghrebian chain in Sicily: Application for non-cylindrical fold-and-thrust belts

Thirteen seismic reflection profiles and field observations have been used to build a three-dimensional watertight geological model of the sub-surface architecture of the Trapanese carbonate platform unit of the Apennine-Maghrebian chain in the Mt. Kumeta and Mt. Rocca Busambra (NW Sicily, Italy). Either a single step or a two-step thrust-fault deformation model is acceptable on the basis of seismic interpretation but the integration of 3D model reconstruction and 3D geomechanical restoration, validates only the scenario with a single stage of deformation. The 3D model highlights along strike variations of the structural style for the Trapanese unit where pre-existing discontinuities (e.g. inherited Mesozoic normal faults) played an important role in the preferential occurrence of hinterland verging structures. In detail, backthrusts (N-verging) are dissected by tear faults along the Mt. Kumeta structure whereas an imbricate backthrust system evolves into thrust along the Mt. Rocca Busambra structure. Shortening estimate indicates low amount of internal deformation affecting the carbonate platform unit (<15%). The combined approach of three-dimensional geological modeling and restoration allowed us to: (i) discriminate the best structural interpretation for the subsurface architecture of the Apennine-Maghrebian chain, detecting issues or inconsistencies in previous seismic interpretations and (ii) propose a valuable tool for hydrocarbon exploration to be applied in other complex structural areas worldwide

Analysis of salt volumes in structural restoration : an example of Santos Basin.

A complexidade da halocinese na por??o central da bacia de Santos envolve expressivas estruturas e depocentros deformados, diferenciados ao longo da dire??o de deforma??o principal. Cinco se??es geol?gicas, com registro estratigr?fico completo na ?rea de estudo, foram restauradas para investigar diferentes estilos de deforma??o, incluindo a evolu??o da falha de Cabo Frio, coerentemente inserida na evolu??o tectonossedimentar da bacia de Santos. O procedimento integrou a restaura??o 2D com tratamento e an?lise 3D, por meio das seguintes etapas: remo??o de camadas, descompacta??o e compensa??o isost?tica flexural; restaura??o desacoplada da tect?nica do sal; conserva??o material (inclusive do sal); recomposi??o da sobrecarga sedimentar quando diferentes taxas de distens?o afetam os dom?nios desacoplados; calibra??o batim?trica do conjunto restaurado e tratamento e an?lise espacial dos resultados. O detalhamento em 14 etapas de restaura??o foi suficiente para tratar a deforma??o de forma n?o cont?nua, minimizou desvios do m?todo e produziu consist?ncia geom?trica e estratigr?fica dos resultados no dom?nio espa?o-tempo. A redistribui??o controlada do sal confirmou os efeitos do aporte sedimentar e as estruturas preexistentes sobre a deforma??o. Os resultados demonstram a import?ncia da reciprocidade dos efeitos de deslocamento lateral por halocinese sobre isostasia, batimetria e descompacta??o, n?o considerada nos programas de restaura??o existentes.Analysis of salt volumes in structural restoration: an example of Santos Basin. Halokinesis complexity in the central portion of Santos Basin involves significant structures and deformed depocenters, differentiated along the tectonic transport direction. Five geological cross-sections with an entire stratigraphic record in the study area have been restored to investigate different deformation styles, including the evolution of Cabo Frio Fault, coherently inserted into the tectonosedimentary evolution of Santos Basin. The procedure combines 2D restoration with 3D treatment and analysis through the following steps: layering removal, decompaction and flexural isostatic compensation; decoupled restoration of salt tectonics; material conservation (including salt); retrieval of the layering when differential strain rates affect uncoupled domains; bathymetric calibration of the restored set, and treatment and spatial analysis of results. Detailing of 14 restoration steps has properly discretized the deformation, minimized procedure deviations, and provided geometric and stratigraphic coherence in the space-time domains. The controlled salt redistribution has confirmed the effects of sedimentary aggradation and pre-existing structures on the strain. The results highlight the reciprocity importance of the effects of the halokinetic lateral displacement on isostasy, eustasy, bathymetry, and decompaction, which was not considered in the existing restoration programs